A major drawback that prevents the large spread use of solar cells is the cost of photovoltaic material, which is presently about 40% to 50% of the final product. There are several approaches that have been tried to minimize the cost of photovoltaic material. The large majority of these approaches are directed to reducing the price of the material by reducing the amount of material used in the solar cell. In other words, fabricate a solar cell on a thin silicon film. The thin silicon films are deposited on top of glasses or on other low cost material, which limit the processing to a low temperature range (<900° C.). Consequently, new fabrication technologies have still to be developed to increase the solar cell efficiency with lower cost silicon material. The efficiencies of thin silicon film solar cells are typically less than 13% and are usually considerably lower than the efficiency of solar grade silicon wafers which are 17% to 22% efficient.
If the starting material comprises scrapped silicon wafers from an MOS FET production line, the wafers have a cost which is just of a few percent of the cost of solar grade Si wafers. Because of the low minority carrier lifetime (<few microseconds) of scrapped silicon wafers, the solar efficiency for photovoltaic conversion of a cell made with this silicon material is less than 14% efficient.